A seat can be defined as an annular part designed to fit into an opening and provide a mating surface for another part. Seats may be made of a metal such as steel, or other material designed to withstand wear. A seat may have a slightly tapered outer diameter designed to be interference fit with a structure such as a pump housing. Its inner diameter may have a frusto-conical section designed to receive a valve of a pump to form a substantially leak-free joint with the valve.
Large volume, high-capacity pumps can have primary structures formed from, for example, cast iron. Pumps constructed in this fashion are used in the oil or natural gas extraction industries to pump drilling fluids to a well hole. Such pumps use check valves, for example, to permit one-way flow of fluids into and out of the pumping chamber, thereby permitting the pump to operate. Check valves operate by sealing and unsealing an opening using a caged, spring loaded check ball, which can be steel, for example. The check valve generally closes by pressing the check ball into the seat by means of the spring pressure. In this way, the seat and check ball may provide a substantially leak-proof seal.